NARRATIVE Defects in nucleotide excision repair (NER) and base excision repair (BER) are associated with genomic instability resulting in a variety of cancers and inherited disorders. The proposed studies will delineate the mechanism by which cells repair lesions that occur through environmental carcinogens and endogenous metabolic errors. The results from our research will have a direct relevance to understanding how mutations in these enzymes cause cancer in order to better direct therapeutic interventions.